The modern energy efficiency mantra dictates that we build new homes to increasingly stringent regulations. We insulate our houses with new materials and retrofit old housing stock to match, sealing every last crack. With undeniable benefits for heating bills and CO2 emissions, what about the impact on the indoor environment?

Internal housing conditions provide an important contribution to good health and wellbeing, and the state of our indoor environments is influenced by a number of factors. Heating, insulation, ventilation and people’s behaviours, along with the type, orientation and geographic location of a property, all work to affect indoor air quality.

Over recent years we’ve witnessed a rise in allergic diseases that can’t be explained by factors such as genetic changes alone. With one in three people suffering from allergies in industrialised countries, there has been an increasing focus on indoor air quality to explain this rise – and a robust body of evidence now suggests that rates of allergic and respiratory disease are linked to poor indoor housing conditions.

This is especially important when considering the amount of time people spend indoors, particularly in vulnerable groups such as the elderly or very young. In the UK the average amount of our time we spend inside is 85%; in the US it’s 90%.

There’s a clear need for high quality research in this area and, at the University of Exeter Medical School’s European Centre for Environment & Human Health, we’ve just published findings that show damp and specific types of mould can pose a significant health risk to people with asthma.

We critically reviewed the findings from 17 studies in eight different countries and found that the presence of several types of mould – among them Aspergillus and the antibiotic-producing Penicillium – can lead to breathing problems in asthma sufferers, worsening their symptoms significantly. It also looks as though mould may actually help to trigger the development of asthma — but research in this area is still in its infancy.

With over 10 varieties found in a typical home, most people may not be aware that moulds are absolutely abundant in our outdoor and indoor environments. If you have a house or flat that suffers from damp, you’re more likely to have more mould.

So what about the causes of damp? The structural integrity and architectural design of a (typically old) building can often lead to water making its way inside. Leaky air-conditioning systems that don’t have overflows correctly installed, or poorly installed and maintained mechanical ventilation systems, can also introduce moisture. A lack of ventilation and heating can then increase the indoor humidity, with this moisture ultimately condensing on cold surfaces and promoting the growth of mould.

Increased household energy efficiency can lead to a number of health benefits and help make a property more affordable to heat. However, efforts to prevent heat loss by reducing ventilation have led to undesired consequences for indoor air quality – increasing indoor dampness and the risk of fungal contamination, which currently affects around 16% of European dwellings. It is also thought that US housing stock suffer from different dampness-related problems compared to European properties, which is yet to be fully explored.

The extent to which a home is heated and ventilated is also largely controlled by the habits of its occupants, and the way people live in their homes varies hugely. For example, some people dry their washing on indoor racks, some shower with the window closed, and many keep their windows and doors closed as much as possible in winter. All of these behaviours can increase the humidity and dampness in a home, with poorer families in particular less likely to maintain adequate ventilation through the winter months — often failing to heat the whole building.

Crucially, we know little about how these behavioural factors contribute to damp and mould in homes that have been retrofitted to make them more energy efficient — an increasingly important issue as huge swathes of old housing stock is revamped.

Our research has highlighted the need for housing providers, residents and healthcare professionals to work together to assess the impact of changes in housing quality and occupant behaviour, and we’re working closely with two Cornish companies to try and find some answers.

In collaboration with social housing provider Coastline Housing we’re aiming to understand how new building practices intended to reduce energy use and fuel poverty — such as improved insulation and energy efficiency — can affect occupant health.

Collecting data through questionnaires with residents and the detailed sampling of homes, we’re hoping to shed light on the complex mix of factors that affect indoor dampness, and communicate best practice to reduce the presence of mould. This award winning enterprise-research partnership is at the cutting edge of built-environment research and has been expanded to include the innovative technology of a second Cornish company, Carnego Systems.

Carnego are helping the team by using their digital monitoring tools to collect real time data (such as temperature and humidity) on the indoor environment. As we attempt to broaden the study’s applications further, we’re also working with several other partners including Community Energy Plus and the Met Office — who will be providing historical weather data to determine how external weather can affect indoor air conditions.

There’s no doubt that energy efficient homes have been an incredibly positive step in the evolution of the country’s housing stock. But the implications for dampness, mould, house dust mites and allergic conditions have been overlooked. We’re ultimately hoping that our findings will go on to inform housing policies and health intervention work aimed at reducing the costs associated with maintaining the built environment, as well as the health and wellbeing of residents throughout the UK.

Richard Sharpe is a PhD researcher at the European Centre for Environment & Human Health, he has received funding from the European Social Fund Convergence Programme for Cornwall and the Isles of Scilly.

Nicholas Osborne PhD is an environmental epidemiologist at the European Centre for Environment & Human Health at the University of Exeter Medical School. He has and is receiving funding from MRC, NERC, ESRC and NIHR as well as the EU.

I’d be interested to know how flooring in particular affects mold and dust levels. I have fairly severe allergies towards both and have lived in rentals with carpets, hardwood or laminate flooring, or a mix of both. My doctors have always told me to aim to live in places without carpet, but it’s near impossible to find rentals without any carpet whatsoever. It would be cool to see how flooring type affects the growth of allergy-causing microbes, although I’m sure it’s been done and I’ve just missed the memo!

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